From: Jeremie Dimino <jdimino@janestreet.com>
To: "Christoph Höger" <christoph.hoeger@tu-berlin.de>
Cc: caml users <caml-list@inria.fr>
Subject: Re: [Caml-list] why is this definition less general?
Date: Thu, 27 Aug 2015 11:11:23 +0100 [thread overview]
Message-ID: <CANhEzE7dZjLXbqd=J7Z_z36rRugJyPZCocN=+T+KX0sOEraJ2A@mail.gmail.com> (raw)
In-Reply-To: <55DEDF9B.5020006@tu-berlin.de>
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On Thu, Aug 27, 2015 at 10:59 AM, Christoph Höger <
christoph.hoeger@tu-berlin.de> wrote:
> Obviously, 'a is bound by its first occurrence in the type annotation,
> here. Can someone explain this behavior?
In a type annotation, the scope of variables is only the type annotation.
So in your example the ['a] in the annotation of [a_to_opt] and the ['a] in
the annotation of [None] are distinct. To refer to the same type, you need
to use a local abstract type:
let rec a_to_opt : type a. (a -> a option) = fun x -> (None : a
option
)
--
Jeremie
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prev parent reply other threads:[~2015-08-27 10:11 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-27 9:59 Christoph Höger
2015-08-27 10:11 ` Jeremie Dimino [this message]
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